Dielectric interconnect structures and methods for forming the same

ABSTRACT

Dielectric interconnect structures and methods for forming the same are provided. Specifically, the present invention provides a dielectric interconnect structure having a noble metal layer (e.g., Ru, Ir, Rh, Pt, RuTa, and alloys of Ru, Ir, Rh, Pt, and RuTa) that is formed directly on a modified dielectric surface. In a typical embodiment, the modified dielectric surface is created by treating an exposed dielectric layer of the interconnect structure with a gaseous ion plasma (e.g., Ar, He, Ne, Xe, N 2 , H 2 , NH 3 , and N 2 H 2 ). Under the present invention, the noble metal layer could be formed directly on an optional glue layer that is maintained only on vertical surfaces of any trench or via formed in the exposed dielectric layer. In addition, the noble metal layer may or may not be provided along an interface between the via and an internal metal layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In general, the present invention provides dielectric interconnectstructures and methods for forming the same. Specifically, the presentinvention provides an interconnect structure having a noble metal layerthat is formed directly on a modified dielectric surface forapplications such as Back End of the Line (BEOL) applications.

2. Related Art

Recently, noble metals such as Ruthenium (Ru) have emerged as analternative liner material for Copper (Cu) integration for multiplereasons. For example, Ru deposition can be done by both Chemical VaporDeposition (CVD) and Atomic Layer Deposition (ALD) techniques. Moreover,Cu has good adhesion to Ru. In addition, a Ru—Cu system isthermodynamically stable and has been reported to be immiscible. Stillyet, Ru does not oxidize easily and has a fairly low bulk resistivity.The low resistivity of Ru is an important feature for it to enabledirect electroplating of Cu.

Some advantages of adopting noble metals for Cu interconnectapplications include the following: (1) better technology extendibilityvs. current Physical Vapor Deposition (PVD) Tantalum-Nitride (Ta(N))technology; (2) conformal deposition from ALD and CVD; (3) capable forCu direct plating; (4) better electrical performance; and (5) thinnerliner layer results in more Cu volume. Unfortunately, despite excellentadhesion strength between Cu and Ru, experimental results revealed pooradhesion between the Ru to dielectric interface. It is likely that Ru, anoble metal, bonds weakly with Carbon (C) and Oxygen (O). This could bea fundamental problem with deposition of Ru directly onto a dielectricsubstrate. Because of the poor Ru/dielectric adhesion issue, waferpeeling problems were observed during Cu electroplating and CMP, thusinhibiting adoption of this metallization scheme into manufacturing.Referring now to FIG. 1, a table 10 of adhesion energy (J/m²) forvarious interfaces is depicted. As shown, PVD of Cu on Ru, plated Cu onRu, Ru on TaN, and PVD of Cu on Ta all exhibit high adhesion energy(e.g., >20 J/m²). However, noble metal to dielectric interfaces such asRu on dense dielectric, and Ru on porous dielectric exhibit low adhesionenergy (e.g., <3 J/m²).

Heretofore, attempts have been made at solving the aforementioned noblemetal to dielectric interface adhesion issue. Referring to FIGS. 2A and2B, two such approaches are shown. Specifically, FIG. 2A shows adielectric interconnect structure 26 having a noble metal layer 16(e.g., Ta). However, in order to achieve sufficient adhesion, betweennoble metal layer 16 and exposed dielectric layer 14, a glue layer 12was required at all noble metal to dielectric interfaces. This includedboth horizontal and vertical surfaces of trenches 20A-B and via 22.Moreover, the dielectric interconnect structure 12 of FIG. 2A appliedglue layer 12 along a horizontal interface 18 between via 22 andinternal metal layer 24. FIG. 2B shows dielectric interconnect structure26 in which glue layer 12 is similarly applied on all interfaces betweennoble metal layer 16 and exposed dielectric layer 14 (e.g., includingboth horizontal and vertical surfaces of trenches 20A-B). However,dielectric interconnect structure 26 lacks glue layer 12 along interface18 between via 22 and internal metal layer 24. The attempts shown inFIGS. 2A-B both suffer from disadvantages including requiring glue layer12 to be present along all noble metal to dielectric interfaces.

In view of the foregoing, there exists a need for a solution that solvesat least one of the problems/disadvantages of the existing art.

SUMMARY OF THE INVENTION

In general, the present invention provides dielectric interconnectstructures and methods for forming the same. Specifically, the presentinvention provides a dielectric interconnect structure having a noblemetal layer (e.g., Ru, Ir, Rh, Pt, RuTa, and alloys of Ru, Ir, Rh, Pt,and RuTa) that is formed directly on a modified dielectric surface. In atypical embodiment, the modified dielectric surface is created bytreating an exposed dielectric layer of the interconnect structure witha gaseous ion plasma (e.g., Ar, He, Ne, Xe, N₂, H₂, NH₃, and N₂H₂).Under the present invention, the noble metal layer could be formeddirectly on an optional glue layer that is maintained only on verticalsurfaces of any trench or via formed in the exposed dielectric layer. Inaddition, the noble metal layer may or may not be provided along aninterface between the via and an internal metal layer.

A first aspect of the present invention provides a method forfabricating a dielectric interconnect structure, comprising: providingan interconnect structure having an exposed dielectric layer; creating amodified dielectric surface by treating the exposed dielectric layerwith a gaseous ion plasma; and depositing a noble metal layer directlyon the modified dielectric surface.

A second aspect of the present invention provides a method forfabricating a dielectric interconnect structure, comprising: providingan interconnect structure having at least one trench in an exposeddielectric layer; depositing a glue layer on the exposed dielectriclayer; removing the glue layer from at least one horizontal surface ofthe exposed dielectric layer by treating the glue layer with a first iongaseous plasma; creating a modified dielectric surface by treating theexposed dielectric layer with a second gaseous ion plasma after removingthe glue layer; and depositing a noble metal layer directly on themodified dielectric surface.

A third aspect of the present invention provides a dielectricinterconnect structure, comprising: a modified dielectric surface formedon an exposed dielectric layer, the exposed dielectric layer having atleast one trench; and a noble metal layer deposited directly on themodified dielectric surface.

A fourth aspect of the present invention provides a dielectricinterconnect structure, comprising: an exposed dielectric layer havingat least one trench and at least one via; a glue layer formed onvertical surfaces of the at least one trench and the at least one via; amodified dielectric surface formed on a horizontal surface of theexposed dielectric layer; and a noble metal layer deposited directly onthe modified dielectric surface and the glue layer.

Therefore, the present invention provides dielectric interconnectstructures and methods for forming the same.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a table of adhesion energy (J/m²) measurements for variousinterfaces according to the prior art.

FIGS. 2A-2B show dielectric interconnect structures according to theprior art.

FIGS. 3A-H show processing steps for forming a dielectric interconnectstructure according to one embodiment of the present invention.

FIGS. 4A-E show processing steps for forming a dielectric interconnectstructure according to another embodiment of the present invention.

It is noted that the drawings of the invention are not to scale. Thedrawings are intended to depict only typical aspects of the invention,and therefore should not be considered as limiting the scope of theinvention. In the drawings, like numbering represents like elementsbetween the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, the present invention provides dielectricinterconnect structures and methods for forming the same. Specifically,the present invention provides a dielectric interconnect structurehaving a noble metal layer (e.g., Ru, Ir, Rh, Pt, RuTa, and alloys ofRu, Ir, Rh, Pt, and RuTa) that is formed directly on a modifieddielectric surface. In a typical embodiment, the modified dielectricsurface is created by treating an exposed dielectric layer of theinterconnect structure with a gaseous ion plasma (e.g., Ar, He, Ne, Xe,N₂, H₂, NH₃, and N₂H₂). Under the present invention, the noble metallayer could be formed directly on an optional glue layer that ismaintained only on vertical surfaces of any trench or via formed in theexposed dielectric layer. In addition, the noble metal layer may or maynot be provided along an interface between the via and an internal metallayer.

Referring now to FIGS. 3A-3H, the process steps involved with forming adielectric interconnect structure according to one embodiment of thepresent invention are shown. Specifically, referring to FIG. 3A, a postetching process is performed to form at least one trench 42A-B and atleast one via 44 (only one via is shown for illustrative purposes) in anexposed dielectric layer 40 (e.g., SiO₂, SiCOH, SiLK, etc.) ofdielectric interconnect structure 30. As further shown, exposeddielectric layer 40 is formed on a capping layer 38 (e.g., NBLoK, SiC,Si₄NH₃, SiO₂, etc.), which itself is formed on an unexposed dielectriclayer 32 (e.g., SiO₂, SiCOH, SiLK, etc.). In addition, an internal metallayer 36 (e.g., Cu, Al(Cu), ect.) is formed in unexposed dielectriclayer 32, and a barrier layer 34 (e.g., Ta(N), Ti(N), Ru, W, etc.) isformed between internal metal layer 36 and unexposed dielectric layer32.

In FIG. 3B, a glue layer 46 (e.g., Ta(N), ect.) is formed (e.g., throughdeposition) on the outer surface of exposed dielectric layer 40. Thisincludes initially forming glue layer 46 in trenches 42A-42B and via 44.In FIG. 3C, dielectric interconnect structure 30 is treated with a firstgaseous ion plasma 31 (e.g., Ar, He, Ne, Xe, etc.) to remove glue layer46 from any horizontal surfaces of exposed dielectric layer 40,including horizontal surfaces of trenches 42A-B and via 44. Thereafter,dielectric interconnect structure 30 is treated with another gaseous ionplasma 33 (e.g., Ar, He, Ne, Xe, N₂, H₂, NH₃, and N₂H₂, etc) to create amodified dielectric surface.

As shown in FIG. 3D, a modified dielectric surface 48 now exists alongeach horizontal surface of exposed dielectric layer 40 (e.g., whereverglue layer 46 no longer exists). This includes horizontal surfaces oftrenches 42A-42B. Referring to FIG. 3E, once modified dielectric surface48 is formed, a noble metal layer 50 (e.g., Ru, Ir, Rh, Pt, RuTa, alloysthereof, etc.) will be formed (e.g., through deposition) directly onglue layer 46 (i.e., where still existing) and directly on modifieddielectric 48. Specifically, as shown in FIG. 3E, noble metal layer 50is formed all along an outer surface of dielectric interconnectstructure 30, including within trenches 42A-42B and via 44. Theformation of modified dielectric surface 48 provides improved adhesionbetween exposed dielectric layer 40 and noble metal layer 50 that wasnot previously provided. Moreover, unlike previous approaches, theembodiment of FIGS. 3A-3H does not require the use of a glue layer onhorizontal surfaces in which the noble metal layer is to be formed.

Once noble metal layer 50 has been formed as shown, additionalprocessing steps can be performed such as filling trenches 42A-42B andvia 44 with a conductive material 52 (e.g., Cu, Al, etc.) as shown inFIG. 3F, and then performing post CMP as shown in FIG. 3G to yield afinalized dielectric interconnect structure 54. As can be seen in FIG.3G, dielectric interconnect structure 54 includes a noble metal layer 50formed directly on glue layer 46 (i.e., where still existing), anddirectly on modified dielectric layer 48.

Noble metal layer is also shown in FIG. 3G as being formed along aninterface 37 between via 44 and internal metal layer 36. However, thisneed to be the case. For example, as shown in FIG. 3H, noble metal layercan be lacking (e.g., entirely avoided) along interface 37 between via44 and internal metal layer 36.

Referring now to FIGS. 4A-4E, the process steps involved with forming adielectric interconnect structure according to another embodiment of thepresent invention are shown. As will be shown, the embodiment of FIGS.4A-4E is similar to that of FIGS. 3A-3H only that glue layer 46 is notformed at all. Specifically, referring to FIG. 4A, a post etchingprocess is performed to form at least one trench 42A-42B and at leastone via 44 (only one via is shown for illustrative purposes) in anexposed dielectric layer 40 (e.g., SiO₂, SiCOH, SiLK, etc.) ofdielectric interconnect structure 30. As further shown, exposeddielectric layer 40 is formed on a capping layer 38 (e.g., NBLoK, SiC,Si₄NH₃, SiO₂, etc.), which itself is formed on an unexposed dielectriclayer 32 (e.g., SiO₂, SiCOH, SiLK, etc.). In addition, an internal metallayer 36 (e.g., Cu, Al(Cu), etc.) is formed in unexposed dielectriclayer 32, and a baffler layer 34 (e.g., Ta(N), Ti(N), Ru, W, etc.) isformed between internal metal layer 36 and unexposed dielectric layer32.

In FIG. 4B, instead of first forming and then selectively removing aglue layer as done for the embodiment of FIGS. 3A-3H, dielectricinterconnect structure 30 is treated with gaseous ion plasma 33 (e.g.,Ar, He, Ne, Xe, N₂, H₂, NH₃, and N₂H₂, etc) to immediately create amodified dielectric surface 48 along all outer surfaces (i.e., on bothvertical and horizontal surfaces) of exposed dielectric layer 40,including in trenches 42A-42B and via 44.

Referring to FIG. 4C, once modified dielectric surface 48 is formed, anoble metal layer 50 (e.g., Ru, Ir, Rh, Pt, RuTa, alloys thereof, etc.)will be formed (e.g., through deposition) directly on modifieddielectric 48. Specifically, noble metal layer 50 is formed all alongthe outer surface of dielectric interconnect structure 30, includingwithin trenches 42A-42B and via 44. As indicated above, the formation ofmodified dielectric surface 48 provides improved adhesion betweenexposed dielectric layer 40 and noble metal layer 50 that was notpreviously provided. Moreover, the embodiment of FIGS. 4A-4E does notrequire the use of any glue layer (i.e., does not require the use of aglue layer on any or all horizontal and vertical surfaces on which thenoble metal layer is to be formed).

Regardless once noble metal layer 50 has been formed as shown,additional processing steps can be performed such as filling trenches42A-42B and via 44 with a conductive material 52 (e.g., Cu, Al, etc.),and then performing post CMP to yield a finalized dielectricinterconnect structure 58 as shown in FIG. 4D. Although noble metallayer 50 is also shown in FIG. 4D as being formed along an interface 37between via 44 and internal metal layer 36, this need to be the case.For example, as shown in FIG. 4E, noble metal layer 50 can be lacking(e.g., entirely avoided) along interface 37 between via 44 and internalmetal layer 36.

Therefore, the multiple embodiments of the present invention provide atleast one dielectric interconnect structure having a modified dielectricsurface for providing improved adhesion between a noble metal layer 50and a dielectric layer 40.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to aperson skilled in the art are intended to be included within the scopeof the invention as defined by the accompanying claims. For example, thedielectric interconnect structures 54 and 58 are shown includingmultiple trenches 42A-42B and a single via 44. However, it is understoodthat dielectric interconnect structures 54 and 58 can include anyquantity thereof (e.g., at least one trench and at least one via).

1. A method for fabricating a dielectric interconnect structure,comprising: providing an interconnect structure having at least onetrench in an exposed dielectric layer; depositing a glue layer on theexposed dielectric layer; removing the glue layer from at least onehorizontal surface of the exposed dielectric layer by treating the gluelayer with a first ion gaseous plasma; creating a modified dielectricsurface by treating the exposed dielectric layer with a second gaseousion plasma after removing the glue layer; and depositing a noble metallayer directly on the modified dielectric surface.
 2. The method ofclaim 1, the noble metal layer being selected from a group consisting ofRu, Ir, Rh, Pt, RuTa, and alloys of Ru, Ir, Rh, Pt, and RuTa.
 3. Themethod of claim 1, the first gaseous ion plasma being selected from agroup consisting of Ar, He, Ne, and Xe.
 4. The method of claim 1, thesecond gaseous ion plasma being selected from a group consisting of Ar,He, Ne, Xe, N₂, H₂, NH₃, and N₂H₂.
 5. The method of claim 1, thedielectric interconnect structure further having at least one via in theexposed dielectric layer.
 6. The method of claim 5, the noble metallayer lacking along a bottom surface of the at least one via.